Hart & Cooley 16 Series 6" Round Ceiling Diffuser (Fits a 6" Hole in the Ceiling) Fits a 6" round hole in ceiling; overall outside diameter is 9-15/16" Step-down diffuser rings deflect air stream 360 degrees Bright White finish; All-steel construction 6" Butterfly Damper for this Diffuser (# 013220) Sold Separately Three mounting holes to securely fasten to the ceiling; screws included